'This Is Us' fans are in shock over that major blowout fight on the season finale

The Season 4 finale of This Is Us moved the Pearson family storyline further into the future, and there is a lot to unpack, so let's just jump right into it.

After Kevin found out that Randall guilt-tripped Rebecca into doing the clinical trial in St. Louis for her Alzheimer's, the two Pearson brothers verbally duked it out and a lot of shots were fired.

"This whole narrative that you keep spinning, this narrative that you took care of the family, where the hell did that come from?" Kevin asked Randall. "All I know is, if I had been there, I would've walked through literal fire and I would've pulled that man out."

Randall responded saying, "Well, Kev, I guess we'll never know, because you weren't there. And he died ashamed of you. And I think that's the part that really gets you, isn't it? The shame that he felt for you and the pride that he felt for me. I mean, you're not even chasing Dad's shadow, Kevin. You're chasing mine. But you'll never be him, and you'll never be me, because you'll never know what it's like to devote yourself to anyone other than yourself. You'll pretend, but it'll just be a performance. A tired, stale performance. Like all of your performances." That's when Kevin hit back even further below the belt.

"You know, I used to think the worst thing that happened to me was the day that Dad died. It's the day they brought you home. Hand to God, Randall, the worst thing that ever happened to me was the day they brought you home," said Kevin to Randall.

Series creator Dan Fogelman previously stated in an interview that viewers would find out the reason why Kevin and Randall aren't speaking to each other in the future and, following the savage argument that went down between the two, we now know why. Actor Sterling K. Brown also confirmed the revelation, when he shared this to his social media.

As for This Is Us fans, they were in total shock over the major shade Kevin and Randall were throwing at each other, while others started to realize that this is, in fact, what drives the brothers apart.

Randall and Kevin right now... I'm surprised no one threw a punch 'cause every SECOND of that argument was laced with fighting words. Every bit of that was hurtful good god #ThisIsUspic.twitter.com/jvkAV7yrxP

As for what to expect in Season 5, per usual, the season finale ended with a lot of new clues about where the Pearson family storyline is headed, while leaving fans with more unanswered questions. Here's what you need to know.

Kate and Toby have decided to have a second baby via adoption, who we later find out is a girl. Madison is pregnant with Kevin's twins. Yes, you read that right — twins. And Kevin is all in.

"I'm so sick of chasing ghosts," Kevin told Madison. "I'm tired of doubting myself. I'm all in, Madison. Whatever you need, I am all in. I want this. I want to be a father. I think I'd be great at it. The love of my life will be my child."

In the final scene of the episode, which flashed forward to the future as Kevin, Randall and Uncle Nicky sit at Rebecca's bedside, we also learn that both Kevin and Nicky are married. However, to whom each are married was left up in the air as both Madison and Miguel were not present in the room.